[Preface]

At the beginning of May, at the 26th China International Bicycle Exhibition, Traveler's 2016 new product launch attracted strong attention from many media, riders and relevant practitioners. Traveler also made several CCTV news reports, which can be said to be an extremely successful product launch.

As a loyal fan of a traveler, the author also participated in the early warm-up activities of the press conference. A number of new product quiz posters released by the official Traveler in advance have really lifted the appetite of many riders. In the face of the large-scale campaign, the author could not guess that the new product is a new frequency pedal, after all, it is only a few months before the release of the first generation of Bluetooth SC frequency pedal. Car riders guess that everything is available, such as helmets, frames and shoes locks. At the beginning, the author guessed that it should be a relatively high-value hardware new generation vehicle, because the scale of the campaign is really not like a small event.

However, the final release was a small and delicate shark fin frequency pedal, 3D road book function and the competition platform, which was unexpected. Later, the author was lucky to Love to play computer games I got the opportunity to assess shark fins. However, due to continuous work and business trips, the report has been delayed so far. I'm really sorry.

[Unpacking]

The outer packaging of the second generation "fin" is much better than that of the first generation of frequency pedal. The pattern of shark fin is printed on the black paper box, following the current trend of extreme simplicity, while the packaging of the first generation is just a paper bag, showing a sense of cheapness.  

However, the paper texture used by the carton is general, and it is slightly uneven when looking closely. There is still a distance between the carton and the tall one visually.

Both sides of the box are sealed with the white logo of the traveler, which is concise and clear.

Of course, there are also logo stickers of our computer/Lei Feng.

Open the box, and the hardware body of the "shark fin" quietly lies there to be a beautiful man.

The black sponge base of the inner box provides a good buffer for the product entity, and no longer worries about the violent transportation of express delivery.

"Shark fin" has excellent industrial design, which is small, exquisite and attractive. It is a world away from the first generation of frequency pedal. People who do not know the history of the product will hardly recognize that they are from the same school. I give full marks for this design. It can be said that this is the most excellent bicycle frequency pedal with industrial design on the market.

The three white lines at the sharp corner of the tail are the positions of the wheel rim sensor, which are used to sense the number of times the wheel rim has turned, so as to calculate the speed and distance.

The three white lines at the sharp corners of the mouth are the position of the pedal frequency sensor, which is used to sense the number of turns of the crank, so as to calculate the pedal frequency data of riding.

The bottom rubber pad is used to install the "shark fin" at the lower part of the frame, which is the saddle of the shark fin.

Putting the whole "shark fin" on the iPod shuffle, it can be seen that it is indeed very compact, and the aerodynamic design of the "shark fin" not only has a beautiful appearance, but also focuses on aerodynamic research and design to optimally reduce the wind resistance of riding.

The "shark fin" needs to be used together with two magnets, one is the stepping magnet and the other is the rim magnet, which respectively correspond to the stepping and rim sensors we mentioned above.

The traveler attached two magnets to each of the two kinds of magnets, so as to avoid the sensitive response caused by the short sensing distance of some frames. The bottom of the stepping magnet can have a "line" logo, and the top is a magnet.

The design of the rim magnet is also much improved than that of the first generation of frequency stepping device. The stability of the tightness details of the screw locking is greatly improved, and the occasional deviation of the previous generation of magnet will not occur.

The back is where the heart of the "shark fin" is located. It is powered by C2032 button battery. The power consumption is also optimized very well. It is said that a button can last for up to half a year.

Installation

The installation method of shark fin is the same as that of the first generation frequency pedal. The installation sequence should be to install the crank magnet first, then determine the installation position of the main frequency pedal according to the position of the crank magnet, and then determine the installation position of the wheel rim magnet according to the position of the wheel rim inductor of the frequency pedal.

First, install the frequency stepping magnet and attach it to the crank. If the induction is not sensitive, both magnets can be used.

Secondly, determine the position of the frequency pedal, and fix the frequency pedal on the frame with a tie belt.

Finally, install the rim magnet and align this sticker with the rim sensor.

Connect the APP of the traveler, set the wheel rim parameters, and get it done.

[Analysis]

Compared with the first generation of walkers' frequency pedal, the innovation of the second generation of walkers' "shark fin" is that more sensors are added to the frequency pedal, expanding the data collection range of the frequency pedal from speed, frequency and mileage to altitude, climb, temperature, air pressure and slope, of which the most important is the introduction of air pressure and temperature sensors.  

as everyone knows, The precision of GPS is limited, especially for the civil GPS equipment with C/A code, especially the elevation precision is less reliable than the horizontal precision. Many riders who use the pedestrian riding APP probably feel the same. The altitude and slope in the riding data of the same riding route are different every time, and even some elevation data are hundreds of meters different, The referential nature of the data really needs to be discussed. This time, the launch of Walker's "shark fin" is aimed at this market pain point, but I still have doubts about the accuracy of Walker's official declaration of "centimeter level". In my early years, I was also a navigation professional. Although my studies have been abandoned, I still feel intuitively that it should be difficult to achieve such accuracy with equipment of 100 yuan level.  

We have learned the relationship between height, air pressure and temperature in middle school physics:

1. The air pressure is the pressure of the atmosphere on the ground. Therefore, in general, the higher the height, the shorter the air column and the smaller the density, so the pressure is lower.

2. The temperature also decreases with the increase of height; The higher the altitude, the colder it is. This is the truth of the so-called "high altitude is too cold".

3. At the same level, there is a negative correlation between air pressure and temperature; On the same level, the relatively hot place is low pressure, and the relatively cold place is high pressure.

In fact, the pressure height formula can be derived from the atmospheric static equation, and the relationship between pressure and height can be obtained.

(Note: the source network of this figure)

On the contrary, the relationship between altitude and pressure change can also be calculated.

(Note: the source network of this figure)

Then combining the relationship between altitude, air pressure and temperature, we can get an altitude data. Of course, the algorithm process is complex. Usually, the standard atmospheric pressure is different in each region, and this data is changing all the time. Rain, wind, snow, and even cloudy will change the standard atmospheric pressure! Through cooperation with professional weather service agencies, the walkers can obtain the standard atmospheric pressure value of the movement location, and synchronize this data to the fin in real time during the movement.  

Now, in addition to an imprecise height value obtained by GPS, the shark fin also has the second altitude value calculated by air pressure and temperature. In addition, according to the official statement of the voyager, with the help of the voyager's altitude database of more than 250 million kilometers as a powerful basic spatial geographic data, combined with the filtered GPS longitude and latitude data, Retrieve the altitude data of the corresponding location in the database to obtain the third altitude value. These three altitude values, through a set of filtering algorithm of the traveler himself, will get a relatively reliable altitude and provide it to the user. What is the precision? Let's feel it through practical experience.

Note: For the calculation of stepping frequency, speed and distance, the principle of shark fin is the same as that of the first generation. Please refer to the official In this paper, we will focus on the comparative evaluation of the altitude of the new function of "shark fin".

[Actual measurement]

1、 Commissioning

Since this evaluation will compare the performance of two generations of frequency pedals on the same vehicle, the author specially installs two frequency pedals on the same vehicle. Although they are two frequency pedals, we know that only one pair of magnets is enough through the above principle analysis, This can also ensure that the crank and wheel rim will not interfere with the frequency pedal when they cross the frequency pedal because the two magnets are too close.

Why is the second generation shark fin facing inward? Think about the technical principle of the frequency pedal.

In this way, on one bicycle, two pacemakers of the same teacher and brother of the traveler are installed at the same time, and two mobile phones are collocated at the same time. The traveler app is installed separately. The iPhone 6+first generation pacemaker is the configuration originally used by the author, and will continue to be retained; In addition, Android Meizu note2+second generation shark fin is the new combination of the traveler that the author has re registered. From the following video (left iphone6+generation 1 frequency pedal, right Meizu+generation 2 shark fin), the response of generation 2 shark fin is faster than that of generation 1. The data of frequency pedal data is basically the same, but the generation 1 delay is a little longer.

2、 Actual measurement on the road: southeast coast of Fujian

[Sampling point A: Jiefang Bridge]

Starting from the Taijiang River and passing the first bridge, Jiefang Bridge, is the first big stone bridge across the Minjiang River. The Minjiang River is also the mouth of the sea. Based on the sea level elevation of 0, the elevation here should be slightly higher than the sea level. The coordinate elevation measured on the map is 2m, which is also consistent with common sense. The most referenced calibration value is reliable.

Compared with the 13.53m altitude of the first generation walker, the 2.5m accuracy of the second generation shark fin is obviously closer to the actual situation.

Summary A: Second generation shark fin win first generation frequency pedal

Ride along Nanjiangbin Avenue, pass by Fanchuanpu Catholic Church, carefully think about coming to Rongcheng for nearly a year, often pass by, but never stop, stop by the roadside to have a look, it's really beautiful.

Continue to ride to the Gushan Bridge and stop under the Gushan Bridge.

[Sampling point B: downstream of Gushan Bridge]

This is located at the edge of the Minjiang River at the mouth of the sea, about 1m above the water surface, and the coordinate altitude measured on the map is 1m.

Compared with the altitude of 3.51m of the first generation of walkers, the accuracy of 0.8m of the second generation shark fin is closer to the altitude measured on the map.

Summary B: Generation II shark fin win generation I frequency pedal

[Sampling point C: Nanjiangbin Road under Gushan Bridge]

Ride your bike under the Gushang Bridge, where the height from the sampling point B is slightly increased, and the elevation difference is only several meters through visual inspection. The coordinate altitude measured on the map is 5m.

Compared with the 11.71m altitude of the first generation of walkers, the 4.3m data accuracy of the second generation shark fin is still significantly higher than that of the first generation of walkers.

Summary C: Second generation shark fin win first generation frequency pedal

[Sampling point D: on Gushan Bridge]

Ride the bicycle along the steps to the Gushan Bridge. Since the altitude is not shown on the map, check the relevant data of the Gushan Bridge: Class II inland waterway (and the navigation of 1000 ton seagoing ships), with a clearance of 24m (height) × 160m (width), and the maximum navigation water level of 7.126m. The height of the bridge is about 5-7 floors by visual inspection, and it should be about 17.5-27m by 3.5-4.5m building height calculation. It seems that the data of 24m bridge height can still be used as reference data.

Compared with the 34.67m altitude of the first generation frequency pedal, the 14.6m data accuracy of the second generation shark fin cannot reflect the real situation, because according to the difference between point D and point C, we can calculate the 10m bridge height of the second generation shark fin compared with the 23m bridge height of the first generation frequency pedal, and the measured height of the shark fin is obviously lower than the actual situation.

Summary D: first generation frequency pedal win second generation shark fin

[Sampling point E: Beijiangbin Road under Gushan Bridge]

Ride along the Gushan Bridge from south to north, and ride down the steps to reach the Beijiangbin Road under the Gushan Bridge. This should be the same as the elevation of point C, because two points C and E are on both sides of the bridge, basically on the same horizontal plane, and the elevation measured on the map is 6m.

Compared with the 14.62m altitude of the first generation of walkers, the data of the second generation of shark fins is - 24m altitude, which is obviously a wrong data. Compared with the data of point C, the data of the first generation of walkers is relatively reliable.

Summary E: Generation I frequency pedal win Generation II shark fin

Compared with the data pk of the above five sampling points (the author's test is in an imprecise test environment, which can only be used as a reference), the second-generation shark fin won in three sampling points, and two sampling points fell behind. The author has a question here. Theoretically, the second-generation shark fin increased or decreased the pressure and temperature sensors, It is reasonable to get a more accurate altitude data through the filtering algorithm, but the actual experience is not flexible. Maybe the author has some problems in the use. In addition, the author guesses that there is still some room for improvement in the core algorithm, and the stability is not enough. For the official "centimeter" level accuracy, Obviously, it can not reach the actual effect of ultra-high precision. In fact, the research on algorithms is very complex. Simulation is one result, but practical application is another. The author also felt the same feelings when working on integrated navigation simulation algorithms in college.

According to the above comparison of cycling data, it can be seen that the cycling mileage, pedal frequency and speed data of the first and second generations are basically the same, so why is the difference between average speed and average pedal frequency large, because the second generation has optimized the calculation of sports time (App The timing is more accurate, and there will be no situation that the cycling has stopped before but the movement time is still timing, so the reference in average speed and average tread frequency is stronger.

Overview

The second generation shark fin of Walker has a strong sense of design. The shape of the shark fin is an aerodynamic design prototype, which gives full marks for its appearance. The air pressure and temperature sensors are added on the basis of the first generation frequency pedal, providing more basis for the altitude data. Although the altitude data in the actual experience cannot be 100% accurate, under the condition of perfect conditions, Indeed, it can provide more reliable data, but in terms of altitude stability, it is still unable to achieve 100% reliability. Apart from the altitude data, the conventional riding data such as riding frequency, speed and distance are quite reliable. Compared with the riding data of the first generation, it can be found that the distance between the two is similar, but the second generation is more accurate in terms of sports time (the first generation still counts sports time when it stops sometimes), so it is more accurate in terms of average speed and average riding frequency. Admittedly, the performance of the product is not perfect. However, given the price of 147 yuan, the author believes that the shortcomings do not outweigh the merits. It is definitely a user-friendly frequency pedal, which is still worth recommending.